SpaceX Falcon 9 : CRS-11 : June 3, 2017 : DISCUSSION

[DaveS]

The problem I am having with the caliper theory is they made it all the way to orbit in the trunk then got dislodged by separation. I would have expected them to have been dislodged during powered flight and have been sitting on top of the second stage already...

Well, it may very well have dislodged during launch and just been sitting on top of the 2. stage all the way to orbit. Then, after SECO if could have drifted back into the trunk, and then drifted out again during dragon separation.

Exactly. SECO would have acted as a negative force on the calipers launching them forward towards the trunk. Then they bounced off something in the trunk looking like they originally came from it. Example, look at shuttle flightdeck ascent footage of the crew at MECO. They're firmly pressed into their seats by the 3G acceleration and when MECO happens they get launched forward by the instantaneous loss of positive forces.

[Paul Adams]

What would callipers be used for? Why would they be in or near the trunk or second stage during vehicle integration?

[Jim]

Do we know the specs of the trunk with regards to temperature and humidity control? Is it advertised as being temperature and humidity controlled?

This is SAGE-III pre Dragon integration processing.  It is in a clean tent within a clean room.   Do you think they are not going to want temperature and humidity control?

[envy887]

The problem I am having with the caliper theory is they made it all the way to orbit in the trunk then got dislodged by separation. I would have expected them to have been dislodged during powered flight and have been sitting on top of the second stage already...

Well, it may very well have dislodged during launch and just been sitting on top of the 2. stage all the way to orbit. Then, after SECO if could have drifted back into the trunk, and then drifted out again during dragon separation.

Exactly. SECO would have acted as a negative force on the calipers launching them forward towards the trunk. Then they bounced off something in the trunk looking like they originally came from it. Example, look at shuttle flightdeck ascent footage of the crew at MECO. They're firmly pressed into their seats by the 3G acceleration and when MECO happens they get launched forward by the instantaneous loss of positive forces.

There is no "negative force" launching the crew forward, other then the deflection of the flight seats under 3G weight of the crew. Unless the calipers was sitting on something that deflected while accelerating it during launch, it wouldn't be launched forward but simply drift around at SECO.

[2megs]

There is no "negative force" [...]

There's no pusher involved in separating Stage 2 and Dragon, right? They just release the clamps and thrust away on Dracos?

(That's what I'd assumed, but if I'm wrong, then there'd be an equal and opposite force on the second stage.)

Edit: This wasn't a critcism of envy887, who's entirely right about SECO itself not imparting negative forces. But there could be other sources... Does the second stage use cold gas thrusters to create additional space with the Dragon?

[DOCinCT]

That is spin.  It is too deep in the trunk for that.  But if so, then there is something just as troubling, they have a humidity and temperature problem for payloads in the trunk.

Do we know the specs of the trunk with regards to temperature and humidity control? Is it advertised as being temperature and humidity controlled?

Considering that anything going as payload in the trunk is designed for vacuum conditions and temperature extremes, I wouldn't think there are issues with temp/humidity control.

[leetdan]

Considering that anything going as payload in the trunk is designed for vacuum conditions and temperature extremes, I wouldn't think there are issues with temp/humidity control.

Neither of those conditions would involve condensed water.

[launchwatcher]

There is no "negative force" launching the crew forward, other then the deflection of the flight seats under 3G weight of the crew. Unless the calipers was sitting on something that deflected while accelerating it during launch, it wouldn't be launched forward but simply drift around at SECO.

if it was bridged across two points of support during the burn, the caliper's own flex could launch it forward.

[Jim]

Considering that anything going as payload in the trunk is designed for vacuum conditions and temperature extremes, I wouldn't think there are issues with temp/humidity control.

quite the opposite when it comes to humidity on the ground

[Wolfram66]

The problem I am having with the caliper theory is they made it all the way to orbit in the trunk then got dislodged by separation. I would have expected them to have been dislodged during powered flight and have been sitting on top of the second stage already...

Well, it may very well have dislodged during launch and just been sitting on top of the 2. stage all the way to orbit. Then, after SECO if could have drifted back into the trunk, and then drifted out again during dragon separation.

Exactly. SECO would have acted as a negative force on the calipers launching them forward towards the trunk. Then they bounced off something in the trunk looking like they originally came from it. Example, look at shuttle flightdeck ascent footage of the crew at MECO. They're firmly pressed into their seats by the 3G acceleration and when MECO happens they get launched forward by the instantaneous loss of positive forces.

There is no "negative force" launching the crew forward, other then the deflection of the flight seats under 3G weight of the crew. Unless the calipers was sitting on something that deflected while accelerating it during launch, it wouldn't be launched forward but simply drift around at SECO.

Can we go back to Newtonian physics 101 please!. INERTIA is the answer to crew moving forward when Shuttle hits MECO. Just like running into a wall with your car or slamming on the brakes. Observer sees occupant thrust through the windscreen, when it is the occupant's own inertia. Same here. caliper is loose between trunk and S2 being pinned to Top of S2 during acceleration. Acceleration stopped at SECO, unrestrained caliper travels into trunk. caliper either rebounds off trunk insulation in an elastic collision. Dragon separation adds acceleration to Dragon+trunk relative to S2. unrestrained caliper bounces free of trunk on it's own trajectory. i don't see why this is difficult. Q.E.D.

[envy887]

The problem I am having with the caliper theory is they made it all the way to orbit in the trunk then got dislodged by separation. I would have expected them to have been dislodged during powered flight and have been sitting on top of the second stage already...

Well, it may very well have dislodged during launch and just been sitting on top of the 2. stage all the way to orbit. Then, after SECO if could have drifted back into the trunk, and then drifted out again during dragon separation.

Exactly. SECO would have acted as a negative force on the calipers launching them forward towards the trunk. Then they bounced off something in the trunk looking like they originally came from it. Example, look at shuttle flightdeck ascent footage of the crew at MECO. They're firmly pressed into their seats by the 3G acceleration and when MECO happens they get launched forward by the instantaneous loss of positive forces.

There is no "negative force" launching the crew forward, other then the deflection of the flight seats under 3G weight of the crew. Unless the calipers was sitting on something that deflected while accelerating it during launch, it wouldn't be launched forward but simply drift around at SECO.

Can we go back to Newtonian physics 101 please!. INERTIA is the answer to crew moving forward when Shuttle hits MECO. Just like running into a wall with your car or slamming on the brakes. Observer sees occupant thrust through the windscreen, when it is the occupant's own inertia. Same here. caliper is loose between trunk and S2 being pinned to Top of S2 during acceleration. Acceleration stopped at SECO, unrestrained caliper travels into trunk. caliper either rebounds off trunk insulation in an elastic collision. Dragon separation adds acceleration to Dragon+trunk relative to S2. unrestrained caliper bounces free of trunk on it's own trajectory. i don't see why this is difficult. Q.E.D.

Wait a sec, who put a wall up in orbit for Dragon to run into? That was mean!

There's no air resistance at separation, so what exactly is causing Dragon to slow down allowing the caliper's inertia to carry it forward relative to Dragon?

Unless you suspect the calipers has it own little thrusters pushing it forward?

[Scylla]

What does air resistance or lack thereof have to do with anything.

INERTIA-Inertia is the resistance of any physical object to any change in its state of motion (this includes changes to its speed, direction or state of rest). It is the tendency of objects to keep moving in a straight line at constant velocity.

1-Object is in trunk, locked in place by thrust of S2.
2-S2 thrust stops and unrestraind object moves into Dragon trunk due to INERTIA.
3-Object bounces around till Dragon seperation and flies out of trunk.

I really can't understand the difficulty with this concept.

[jpo234]

2-S2 thrust stops and unrestraind object moves into Dragon trunk due to INERTIA.

This would only be true if an external force is applied to S2/trunk. Otherwise inertia applies equally to the whole system S2/dragon/caliper. For the caliper to move relative to S2/trunk it needs a separate force.

[punder]

But, but isn't the inertia the same for the calipers and the stage at SECO?   

It's little random forces that cause things to separate in freefall in vacuum.

Ninja'd!!

[Lar]

(mod) Please be respectful and sensitive about this, and don't propagate rumors needlessly. I think in general you're all doing great, but keep up the good work, thanks

[Scylla]

2-S2 thrust stops and unrestraind object moves into Dragon trunk due to INERTIA.

This would only be true if an external force is applied to S2/trunk. Otherwise inertia applies equally to the whole system S2/dragon/caliper. For the caliper to move relative to S2/trunk it needs a separate force.

Are you saying, when you are in a car and hit the brakes, your movement forward is caused by a seperate force or when you go around a curve the force pushing you to the side is caused by a seperate force?

Please educate me on this non inertial force acting on you and the car separately.

[jpo234]

INERTIA is the answer to crew moving forward when Shuttle hits MECO. Just like running into a wall with your car or slamming on the brakes.

But there is no wall and no brakes. The correct analogy would be going from accelerating you car to cruising. When the acceleration stops, the force that presses you into the seats stops.
You still need your cars engines to replace friction losses, but otherwise inertia would keep the whole system moving at the same speed.

[jpo234]

2-S2 thrust stops and unrestraind object moves into Dragon trunk due to INERTIA.

This would only be true if an external force is applied to S2/trunk. Otherwise inertia applies equally to the whole system S2/dragon/caliper. For the caliper to move relative to S2/trunk it needs a separate force.

Are you saying, when you are in a car and hit the brakes, your movement forward is caused by a seperate force or when you go around a curve the force pushing you to the side is caused by a seperate force?

Please educate me on this non inertial force acting on you and the car separately.

Hitting the brakes is applying a force against inertia. SECO/MECO is switching from acceleration to cruising (e.g. NO external force).

[dawei]

If it was calipers (not ice) and if upon shutdown of the second stage it moved forward from the second stage area to impact somewhere near the top of the trunk is it possible that it could have damaged the Dragon heat shield?  I don't recall if there is a barrier at the top of the trunk or if the heat shield should be visible once cargo is removed?

[eeergo]

Totally right about inertia applying to the whole system.

However

A rocket engine shutting off does not follow a clean square function of "X thrust - 0 thrust". There is a jolt that will propel forward loose stuff in the stack. RD-0110 is a whole different engine, but look at the "zero-G indicator" (aka plush toy) cosmonauts leave dangling in their Soyuz capsules for a very graphic illustration of this phenomenon.

Therefore, it is entirely possible for the thing to have rebounded up from the S2 upper dome to the trunk and then backwards from (this time yes) inertia at Dragon Sep. Or it could just have been lodged in some cranny in the trunk all the way up, and then been dislodged because of the jolt at SECO or separation.

If it is not ice and it flew from the S2 dome forward though, I'd worry about damage to the external payloads.